Blink Rate and Amplitude as New Psychophysiological Indices of Anxiety and Emotion

Spontaneous eye blink rate is an easily acquired biological measure previously associated with task requirements, attention, and emotional state. In the current work, we broadened the scope and investigated 4 measures capturing the temporal dynamics as well as the magnitude of eye blinks – Blink Rate (BR), Blink Amplitude (BA), Blink Rate Variability (BRV) and Blink Amplitude Variability (BAV). A sample of 50 female students was monitored using vertical electrooculogram at rest and while watching emotion-inducing film clips to induce eye blink modulation. 18 short movies were presented to participants and represented six affective categories: Fear, Sadness, Erotic, Compassion, Scenery and Neutral. The proposed blink measures were only moderately intercorrelated in most cases, implying that different specific information is provided by each. Blink characteristics (BR, BA and BRV) collected during film viewing were correlated with self-reported state anxiety, whereas at rest, only the association with BA remained significant. BA was also predicted by trait anxiety; however, the effect size was lower than with state anxiety. While for all the movie categories BR decreased during film presentation compared to the preceding baseline, the distinct affective states were associated with different blinking behavior. For instance, lower BR was observed in fearful and neutral movies, higher BA was associated with erotic clips and a higher BRV was found when watching scenery videos. Overall, our results indicated that BA is a better index for state anxiety, and that BA, BR, BRV and BAV were specific indices for different emotional categories.